Method of operating open-hearth furnaces



May 29, 1951 F. H. BARNES ET AL 2,554,609

METHOD 0F OPERATINGOPEN HEARTH FURNACES Filed Jan. 10, 1948 2 Sheets-Sheet l Il n n FIISQIL.,

FHBB- May 29, 1951 F. H. BARNES ET AL METHoDoF OPERATING OPEN HEARTH FURNAcEs 2 Sheets-Sheet 2 Filed Jan. lO, 1948 Patented May 29, 1951 METHOD" F 'OPERATING' OPEN-HEARTH FURNACES Fred H. Barnes', Charles M. Kay; andtewart'F.

Oakes., Worcester; Mass.,

assignors" to The American Steel' and Wire Company of New Jersey, a corporation of New Jersey Application-January 10, 1948Serial No.1,57.7f

` 4- Claims.

1` This invention relates to a method' of operatingopen hearth furnaces and'more particularly to operatingsuchfurnaces when they are using.

scrap metal as part ofthe charge. In the operationof such furnacesscrap is first charged. into the furnace and melted down,.after which cold or' hot iron vor both are added and the entire charge refined'. Various types of f'uel,V such as gas, oil and tar, are used'in heating the furnace. In some instances a combination of gas and. oil. or tar is used.. This invention relates to' those furnaces inwhich oil or tar are used separately. or'in combination with gas andfor the purpose of thisapplication, any fuel made up in whole Orin partof a liquid will be termed liquid fuel. InV heatingthe charge, the heat is supplied alternately from each end of the furnace and ordinarily a single burner is used at each end of the furnace. In some instances Where gaseous fuels are used, two burners maybe'used at each end ofthe furnace, but these are commonly low pressure burners firing in approximately a hori zontal plane at an angle to the longitudinal center line of the furnace'. The amount of heat required varies at different stages 'of the heat. The desired characteristicsof the'flame are also diiferentat various stages ofthe heat. When using a single liquid fuel' burner it` is' difficult to 'obtain the desired concentrationo'f heat at all times and itis also'diflicultto maintain the correct flame' characteristics;

fla'n'i'er is: preferable while during" the refining` period a' longer luminous flame" is preferred;

In' using" a single-hurnerthel volume of" fuelv is` such` that thecombustion' is somewhat delayed because" the fuel and" air do not' mix" readily;

and as airesult, the -meltingrdownioffthe scrap charge iis`-y delayedbecause.v the'fmax-imum frame:

is increased with an accompanying increase. in.

meltingV rate and'A fuel efliciency. It has been' suggested that air be introduced' around' the During the melting' down period" a sharp, short intense luminous" periphery ofthe. fuel.` outlet', but this does not act tosupply the combustionair'in thedesired manner..

It is an object of this invention to provide a method of firing an open hearth furnace which' compressedy air is introduced into the furnace directly beneath the fuel streamina furnace havingeither a single ordouble burner..

This and other objects will be more apparent after referring to the following. specification and attached drawings', in whichz.

Figure l is a horizontal sectional` view taken at.

theV burner ports;.

Figure 2 is a sectional view taken on .the line Figurev is a longitudinal section through the.

lower burner andauxiliary. air supply Figure. 6 isia sectional-view taken on theline VI`VI of Figure 4;. and

Figure 7 isa sectional View taken onthe line VII-VII of Figure 5.

Referringmore particularly to the drawings, the reference numeralv 2 indicates. the hearth of an open hearth furnace. The ends of the furnace are the same and therefore only one end is shown in the drawings and will be described. herein. A pairof burner tunnels 4 are provided through theend wall 5 and twoliquid fuel burners of conventional design are locatedtherein. The. lower burner. 6 is arranged approximately on the center line of the furnace Withits axis arranged at an angle to. intersect the surface of.

the. charge.. Directly. above the burner 6 is the burner 3 which. is arranged at a steeper angle.

than burner (i so that itsY extended axis will intersect the extended axis ofY burner 6 at. a point beyond the point of intersection of the axis. of burner 6 with the charge. As isusual, the

liquid fuel is atomized withsteam or air and the.

therein'. The opening 30`is on the center line of" the furnace and two openings similar to openings 26 and 28 are located on the opposite side of the center line.

As best shown in Figures 4 through '7, compressed air is introduced into the furnace through a pipe 32 located directly beneath and substantially parallel to the burner 6. As is usual, Water is supplied to the water jacket 34 of the burner E through the water inlet 36, the

water being discharged from the jacket 34 through the pipe 38. The compressed air pipe 32 is preferably surrounded by a pipe 40 which acts as a water jacket and, as shown, is welded to the burner 6, Wafer is introduced into the pipe 40 through the inlet pipe 42 and is discharged through the pipe 44.

The furnace is operated as follows:

Metal scrap is charged into the furnace. burners 6 and 8 are started in operation and compressed air is introduced through the pipe 32. upwardly through the uptake I 6 around the streams of fuel flowing from the burners. The streams of fuel flowing from the burners flow longitudinally into the chamber IB with the stream from the burner 6 being directed downwardly at an angle to impinge on the charge and the stream from the burner 8 being directed above the first stream downwardly at an angle to impinge on the charge at a point beyond the point of impingement of the first stream on the charge. The center lines of the streams of fuel intersect at a Zone be tween oneethird and one-half the length of the furnace (as measured between the burner tips at each end of the furnace) from the burners. In the furnaces in which the method is being used, this zone includes doors 28 and 30 and the space therebetween. Because of the bulkiness of the scrap charge it is advantageous to have the two flames impinge on the charge at different positions and at different angles.

In the furnaces in which the method is being used we have found that the compressed air being delivered to the furnace should have a minimum pressure of 30 pounds per square inch. but better results are obtained when the pressure is increased to 100 pounds per scuare inch or more. At 100 pounds per square inch pressure and one inch diameter opening. 1600 cubic feet of air per minute is introduced at a temperature of approximately 200 E'. The compressed air supplied may be 2 to 20% by weight of the total combustion air being supplied. By supplying air in this manner, combustion starts at the burner tip and progresses gradually until it strikes the charge with the greatest amount of heat being concentrated downwardly on the charge where it is most useful. The advantages of the compressed air are greatest during the melting period, but some advantages accrue at other times.

While we have shown and described the invention relating to supplying compressed air beneath the lower burner of a pair of burners, many of the advantages of the use of the compressed air are obtained when using a single burner. If desired. compressed air can also be used to advantage beneath the top burner. We have found that it is advantageous to provide from 30 to 75% of the fuel through the top burner and the remaining fuel through the lower burner. As compared to the single burner previously used, about 25% more fuel may be used efiiciently with the double burners. On single The air from the checker chamber I4 flows burners about 3.05 pounds of steam are consumed per gallon of oil fired whereas the total steam consumption is about 3.5 pounds per gallon of oil fired when two burners are used, this being approximately a 15% increase per gallon of oil. Due to the increase in fuel consumption, approximately 1290 pounds of steam is consumed per hour with double burners as compared to Y920 pounds on a single burner, this being an increase of approximately 40%. During the rening period, the top burner 8 is shut off and only the lower burner 6 is used. This is necessary because the large amount of heat liberated through the use of the two burners and increased fuel will overheat the roof and walls if there is an insufcient amount of cold charge available to absorb the heat input. Preferably during the refining period the compressed air is shut off and only the lower burner 6 is used.

It will be understood that the furnace will otherwise be operated in the manner normal to such furnaces, that is, it will be reversed at intervals and on each reversal the burners and the air on one end will be shut off and the burners and the air on the other end turned on.

While one embodiment of our invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

We claim:

l. In the method of making steel in the melting chamber of an open hearth furnace which includes the step of charging metal scrap into the furnace, the improvement in the melting step thereof comprising projecting a stream of liquid fuel from a burner into one end of and longitudinally of said chamber, said stream being directed downwardly at an angle to impinge on said charge. introducing a stream of compressed air at a pressure of at least approximately 30 pounds per souare inch into said chamber directly below and substantially parallel to said stream of fuel, said stream of compressed air being substantially the only compressed air introduced adjacent said stream of fuel. and owing into said chamber a stream of preheated air around said streams.

2. The method of burning fuel in the melting chamber of an open hearth furnace which includes the steps of charging metal into the furnace, projecting a stream of liquid fuel from a burner into one end of and longitudinally of said chamber, said stream being directed downwardly at an angle to impinge on said charge, introducing a stream of compressed air into said chamber directly below and substantially parallel to said stream of fuel. said stream of compressed air being substantially the only compressed air introduced adjacent said stream of fuel, and flowing into said chamber a stream of preheated air around said streams, said compressed air constituting approximately between 2% and 20% by weight of the total amount of combustion air supplied.

3. The method of burning fuel in the melting chamber of an open hearth furnace according to claim 2 in which a second stream of liquid fuel is directed into said chamber above the first stream downwardly at an angle to impinge on said charge at a point beyond the point of impingement of the first stream on the charge, and supplying from 30% to 75% of the fuel through the top burner, and the remainder through the bottom. burner.

4. Themethod of burning fuel in the melting chamber rof an open hearth furnace which includes 'the steps of charging metal into the furnace, projecting a stream of liquid fuel from a burner into one end of and longitudinally of said chamber, said stream being directed downwardly at an angle to impinge on said charge, introducing a stream rof compressed air at a pressure of at least approximately 30 pounds per square inch into said chamber directly below and substantially parallel to said stream of fuel, said stream of compressed air being substantially the only compressed air introduced adjacent said stream of fuel, fand owing into said chamber a stream of preheated air around said streams, said compressed airconstituting approximately between 2% and 205% by weight of the total amount of combustion air supplied.

FRED H. BARNES. CHARLES M. KAY. STEWART F. OAKES.

REFERENCES CITED UNITED STATES PATENTS Name Date Kernohan et al. Nov. 4, 1924 Number 6 Number Name Date 1,554,251 Schieldrop Sept. 22, 1925 1,736,675 Steese Nov. 19, 1929 v1,830,574 Thwing Nov. 3, 1931 1,860,045 Mambourg May 24, 1932 1,907,140 Bartholomew May 2, 1933 1,955,589 Leahy Apr. 17, 1934 1,964,544 Trinks June 26, 1934 '2,925,165 Henry Dec. 24, 1935 2,233,916 Creighton Mar. 4, 1941 2,310,454 Mulholland Feb. 9, 1943 2,362,085 Morgan Nov. 7, 1944 y2,385,261 Crowe Sept. 18, 1945 2,412,579 Hauzvic Dec. 17, 1946 12,417,951 Schwartz Mar. 25, 1947 2,446,511 Kerry et al Aug. 3, 1948 2,466,258 Morgan Apr. 5, 1949 2,484,272 Crowe Oct. 11, 1949 A66, published by Steel Publications. Pittsburgh, 

1. IN THE METHOD OF MAKING STEEL IN THE MELTING CHAMBER OF AN OPEN HEARTH FURNACE WHICH INCLUDES THE STEP OF CHARGING METAL SCRAP INTO THE FURNACE, THE IMPROVEMENT IN THE MELTING STEP THEREOF COMPRISING PROJECTING A STREAM OF LIQUID FUEL FROM A BURNER INTO ONE END OF AND LONGITUDINALLY OF SAID CHAMBER, SAID STREAM BEING DIRECTED DOWNWARDLY AT AN ANGLE TO IMPINGE ON SAID CHARGE, INTRODUCING A STREAM OF COMPRESSED AIR METAL RINGS HAVING THEIR ENDS JOINED TOGETHER, THE OUTER OF SAID RINGS BEING SUBSTANTIALLY IN THE SHAPE OF THE SURFACE OF A SPHERICAL ZONE AND THE INNER OF SAID RINGS COMPRISING A BELLED ANNULUS, EACH OF SAID RINGS HAVING A PLURALITY OF SMALL OPENINGS THERETHROUGH, A PLURALITY OF NUTS MOUNTED ON THE INNER SURFACE OF EACH OF SAID RINGS WITH EACH OF SAID NUTS SURROUNDING ONE OF SAID OPENINGS, MEANS FOR SUPPORTING SAID COWL COM- 